This application seeks to achieve two broad objectives: (i) to study the effects of disinhibitory drugs of abuse on (maladaptive) human risk-taking using laboratory behavior-based procedures; (ii) to identify basic behavioral mechanisms operating in individuals (specifically young adults) who show heightened susceptibility to risk taking following use of disinhibitory drugs. Disinhibitory drugs can engender increases in the (otherwise low) frequency of certain behaviors. Use of disinhibitory drugs is associated with a number of risk-taking behaviors leading to harmful outcomes -- including automobile accidents, vandalism, violent crimes, sexual assault, and risky sexual behavior. Importantly, use of disinhibitory drugs and the risky behavior that often follows is prevalent among younger adults. The social and behavioral consequences of drug-mediated risk taking in young adults are thus a considerable public health concern and a vital scientific endeavor. Studying the relationship between disinhibitory drugs and risk-taking behavior under controlled laboratory conditions will provide important scientific information. The experiments in this application propose to investigate changes in risk-taking following acute administration of four drugs abused by young adults: alcohol, marijuana, and the benzodiazepines alprazolam (Xanax) and flunitrazepam (Rohypnol). While many young adults use these drugs, not all abuse them, and not all engage in excessive risk-taking while under the influence. Thus, identification of basic behavioral processes and characteristics involved in risk-taking may help predict those whose behavior is most likely to be unduly influenced by drug use. Each of the four proposed experiments will employ a laboratory-based task to measure risk-taking. This task has been systematically developed over several years, and has been shown to be sensitive to (i) individual differences in risk-taking (in both adolescent and adult populations), and (ii) acute drug effects. Each participant will work on the risk-taking task following acute administration of one of the above-mentioned disinhibitory drugs. Using a within-subject design, a range of doses will administered in order to determine dose-effect relationships. Quantitative analyses of behavior patterns will be used to identify factors that may mediate this relationship.